Using Extensions
Extensions are a way to add libraries to Core Classloader.
Extensions are typically used to enable Wagon providers, used for the transport of artifact between repositories, and plug-ins which provide lifecycle enhancements.
Wagon providers
<project>
...
<build>
<extensions>
<extension>
<groupId>org.apache.maven.wagon</groupId>
<artifactId>wagon-ftp</artifactId>
<version>2.10</version>
</extension>
</extensions>
</build>
...
</project>
Plug-ins which provide lifecycle enhancements
<project>
...
<build>
<plugins>
<plugin>
<groupId>org.apache.felix</groupId>
<artifactId>maven-bundle-plugin</artifactId>
<extensions>true</extensions>
<configuration>
...
</configuration>
</plugin>
</plugins>
</build>
...
</project>